sept, is, i 9 i6 Dwarf Eggs 1023 



small lump of tough membrane resembling shell membrane. The one 

 laid on June 10 contained what appeared to be an empty yolk mem- 

 brane. It will be shown later that a dwarf egg sometimes contains a 

 ruptured yolk membrane from which most of the yolk has escaped, but 

 this membrane contained no yolk. If it was a yolk membrane, all of the 

 yolk had been squeezed out. 



It is of some interest that this bird was a breeder, and the normal 

 eggs laid between February 23 and April 22 were incubated. All but 

 two were fertile, and 44 per cent hatched. It will also be noted that on 

 August 26 both a dwarf egg and a normal egg were produced. 



The dwarf egg and nesting records of this bird seem to indicate some 

 disturbance of the morphology or physiology of the oviduct, which fre- 

 quently but not always interfered with the entrance of a normal yolk or 

 prevented its passage through the duct. Since this bird was sold alive, 

 there is no record of the condition of the sex organs. As in other cases 

 of dwarf eggs without yolk, it is impossible to tell whether the eggs were 

 initiated by a yolk which entered the duct and was then extruded, or 

 whether the fibers of chalazal material or other inclusions were efficient 

 stimuli. 



B. — EVIDENCE FROM THE EGG RECORDS AND AUTOPSY RECORDS OF NORMAL 

 DWARF-EGG PRODUCERS ON WHICH AUTOPSIES WERE PERFORMED 



Attention has already been called to the fact that, while occasional 

 cases occur where dwarf -egg production is due to a permanent disturbance 

 of the reproductive apparatus, it is in general not associated with such a 

 condition. In fact, a dwarf egg may occur at any time in a clutch or 

 litter, the production of normal eggs continuing as if the dwarf had 

 been a normal egg. In these cases the egg records give no hint as to the 

 reason for the production of a dwarf egg. Our only data are obtained 

 from the contents of the egg and the autopsy examination of the repro- 

 ductive organs. Such autopsy records are available for 27 of the 189 

 dwarf-egg producers, which were apparently normal at the time of the 

 production of the dwarf egg. In 4 cases a dwarf egg was found in the 

 oviduct or body cavity at autopsy. Only one of these birds had previ- 

 ously laid a dwarf egg. In 3 cases the bird was killed a few hours after 

 the dwarf egg was laid. Autopsies were made on 20 other cases from 9 

 to 508 days after a dwarf egg was laid. While the general or permanent 

 morphological condition of the sex organs of a dwarf-egg producer is 

 shown by each of these records, the temporary condition of the organs at 

 the time a dwarf egg is produced is shown only by the cases on which 

 autopsies were made while a dwarf egg was in the duct or within a few 

 hours after such an egg was laid. 



At the time of autopsy the sex organs of the birds which had produced 

 a dwarf egg from 9 to 508 days before death were in every stage of repro- 

 55853°— 16 4 



